The four drug sequence, cyclophosphamide, vincristine, F3TdR and papaverine designated as the N-3 has proved effective in inducing remission in patients with disseminated neuroblastoma considered resistent to conventional and experimental drugs and radiation. The drug administration program has undergone some evolution based upon the experience with the first twenty-eight patients. The number and intensity of courses required to totally eliminate the tumor, and further minimization of the morbidity following drug administration and tumor cell lysis remain to be established. The use of in vitro and in vivo (nude mice) tumor - drug sensitivity profiles for each patient has been shown to be feasible and their prospective value will be determined.